2027 ICD-10-CM Diagnosis Code A51.0Primary genital syphilis
ICD-10-CM Codes›A00–B99›A50-A64›A51
- Billable — Valid for Submission
- Not Chronic
A51.0 is a billable ICD-10-CM diagnosis code for primary genital syphilis. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 727 through 728, 742 through 743, 757 through 759. Coders also document this condition as bacterial balanitis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Sexually transmitted infections (excluding HIV and hepatitis).
Code Identity
Code Classification
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Bacterial balanitis
- Infective dermatosis of female genitalia
- Primary genital syphilis
- Primary syphilis
- Syphilitic balanitis
- Syphilitic chancre
- Syphilitic chancre of penis
- Syphilitic chancre of vulva
Instructional NotesGuidance
Instructions from the official ICD-10-CM Tabular List that apply to A51.0: its own notes plus those printed at block A50-A64 and Chapter 1. A note printed at a category, block or chapter applies to every code under it.
Includes
Further defines, or gives examples of, the content of the category.
- diseases generally recognized as communicable or transmissible
Applicable To
Conditions this code is used for: synonyms of the title or, for "other specified" codes, the conditions assigned to it. The list is not exhaustive.
- Syphilitic chancre NOS
Excludes1
Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.
Excludes2
Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.
- human immunodeficiency virus [HIV] disease (B20)
- carrier or suspected carrier of infectious disease (Z22.-)
- certain localized infections - see body system-related chapters
- infectious and parasitic diseases complicating pregnancy, childbirth and the puerperium (O98.-)
- infectious and parasitic diseases specific to the perinatal period (P35-P39)
- influenza and other acute respiratory infections (J00-J22)
Use Additional Code
Add a second code, after this one, to fully describe the condition.
- code to identify resistance to antimicrobial drugs (Z16.-)
Source: CMS ICD-10-CM Tabular List. How to read instructional notes.
Referenced in Other NotesGuidance
Instructional notes printed at other codes that name A51.0, its category, or a range that includes it.
Applicable To 1
These notes mention A51.0.
- O98.1 Syphilis complicating pregnancy, childbirth and the puerperium
Excludes1 2
These codes carry an Excludes1 note naming A51.0: they are not reported together with it, unless the two conditions are unrelated.
Excludes2 1
These codes carry an Excludes2 note naming A51.0: its condition is not part of those codes, and both may be reported when the patient has both.
- Block A65-A69 Other spirochetal diseases
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
syphilitic (primary) A51.0
urethra A51.0
primary See Also: Syphilis, primary; A51.0
Syphilis, syphilitic (acquired) A53.9
bubo (primary) A51.0
chancre (multiple) A51.0
Rollet's A51.0
genital (primary) A51.0
penis (chancre) A51.0
primary A51.0
genital A51.0
vagina A51.0
vulva A51.0
Ulcus See Also: Ulcer;
durum (syphilitic) A51.0
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Chancre
the primary sore of syphilis, a painless indurated, eroded papule, occurring at the site of entry of the infection.
Patient EducationClinical
Syphilis
Syphilis is a sexually transmitted infection (STI) caused by bacteria. It infects the genital area, lips, mouth, or anus of both men and women. You usually get syphilis from sexual contact with someone who has it. It can also pass from mother to baby during pregnancy.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert A51.0 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About A51.0Overview
What is the ICD-10 code for primary genital syphilis?
The ICD-10-CM code for primary genital syphilis is A51.0 (sometimes written as A510). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
Is A51.0 (Early syphilis) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report primary genital syphilis on HIPAA-covered claims from October 1, 2026 through September 30, 2027.
What MS-DRG does A51.0 group to?
When primary genital syphilis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 742, 759, 727, 743, 728, 758, 757, with relative weights from 0.7687 to 1.8448 depending on complications. Higher weights mean higher Medicare reimbursement.
Can A51.0 be reported with N34.1?
Not as a rule. The Excludes1 note at block A50-A64, which applies to A51.0, lists "nonspecific and nongonococcal urethritis (N34.1)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).
What is the ICD-9 equivalent of A51.0?
Under the General Equivalence Mappings, primary genital syphilis converts to ICD-9-CM 091.0 (primary genital syphilis). The mapping is a direct match.
